Multiple temperature measurements coupled with modeling

ABSTRACT

The present invention is directed to, inter alia, systems and methods for calculating a temperature associated with an analyte measurement component of a biosensing instrument (such as a blood glucose monitor), with a test strip that is inserted in a biosensing instrument, or both. The present systems and methods may employ at least two temperature sensors, and the acquired temperature information may be used to modulate data regarding an analyte in a biological sample, thereby providing a more accurate measurement of the analyte.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. Ser. No. 12/603,137,filed Oct. 21, 2009, which claims priority to U.S. Provisional App. No.61/106,994, filed Oct. 21, 2008, both of which are hereby incorporatedby reference in their entireties.

TECHNICAL FIELD

The present invention relates to the detection of analyte levels bymedical diagnostic systems such as blood glucose meters.

BACKGROUND

Biosensing instruments are used for the detection of various analytes(e.g., glucose and cholesterol) in blood samples. For example, bloodglucose meters are medical diagnostic instruments used to measure thelevel of glucose in a patient's blood, and may employ disposable samplestrips having a well or reaction zone for receiving a blood sample. Somemeters include sensor assemblies that determine glucose levels bymeasuring the amount of electricity that can pass through a sample ofblood, while other meters include sensor assemblies that measure howmuch light reflects from a sample. A computer microprocessor of themeter then uses the measured electricity or light from the sensorassembly to compute the glucose level and displays the glucose level asa number.

An important limitation of electrochemical methods of measuring theconcentration of a chemical in blood is the effect of confoundingvariables on the diffusion of analyte and the various active ingredientsof the reagent. For example, analyte readings are influenced by theambient temperature that surrounds the sample well or reaction zone. Aswith any electrochemical sensing method, transient changes intemperature during or between measurement cycles can alter backgroundsignal, reaction constants and/or diffusion coefficients. Accordingly, atemperature sensor may be used to monitor changes in temperature overtime. A maximum temperature change over time threshold value can be usedin a data screen to invalidate a measurement. Absolute temperaturethreshold criteria can also be employed, wherein detection of highand/or low temperature extremes can be used in a data screen toinvalidate a measurement. The microprocessor of a glucose sensor canmake a determination as to whether the temperature of the testingenvironment is within predetermined thresholds, and prohibit a user fromrunning a test if accuracy would be negatively affected. It isimportant, therefore, that any temperature sensing elements of theglucose meter not be affected by heat generated within the glucose meter(e.g., by a backlight liquid crystal display).

The temperature sensing elements of the glucose meter should have accessto the ambient temperature surrounding the meter. In view of thetemperature sensitivity of the biochemical reactions that areinterpreted by a biosensing device, ambient temperature values that areobtained by temperature sensors are directly used during the assessmentof analyte levels in the sample. As a consequence, even relatively minorvariations in sensed ambient temperatures can create fluctuations inbiochemical readings and result in erroneous outputs. Because theoutputs provided by the biosensing device is intended to influence thepatient's decisions regarding, inter alia, dosing of medication, it isvery important that erroneous readings be avoided. Thus, biosensinginstruments should include means for avoiding erroneous outputs thatresult from inaccurate or misleading ambient temperature readings.

Various prior art instruments employ internal or external thermalsensors in order to acquire information about the ambient temperature(see e.g., U.S. Pat. No. 5,405,511; U.S. Pub. No. 2006/0229502), whileother instruments attempt to control the temperature of the reactionzone, and still other devices attempt to obtain indirect measurements ofblood sample temperature by use of complex algorithms that rely upon theuse of an ambient temperature sensor in combination with AC admittancemeasurements (see U.S. Pat. No. 7,407,811).

While sensors that are sensitive to ambient temperature are capable ofrapidly reacting to a temperature change and thereby provide timelyinformation, under certain circumstances this attribute can haveundesired consequences. For example, when a biosensing instrument thatis normally held in a user's hand is placed on a tabletop, a rapidtemperature change may occur that can bias subsequent biochemicalreadings until ambient temperature readings have stabilized. As forinstruments that attempt to control the temperature of the reactionzone, if the biosensing instrument is battery-driven, it becomesimpractical to control the reaction zone temperature as this requirestoo great a power drain from the instrument's battery. Furthermore,certain approaches, such as that described in U.S. Pat. No. 7,407,811 donot provide a universal solution to the problem of estimating ambienttemperature; the approach described in that patent is designed for usewith a specific glucose strip, and if the strip chemistry or stripgeometry changes, the disclosed algorithm must be modified. Thereremains a need for temperature sensing systems that can overcome theseproblems and otherwise improve the accuracy of analyte measurements bybiosensing instruments.

SUMMARY

In one aspect of the present invention, provided are systems comprisinga housing that substantially defines an internal space; an analytemeasurement component that is within the housing or proximate thehousing; a first temperature sensor that is disposed at a first positionwithin the housing and is in thermal communication with a heat source; asecond temperature sensor that is disposed at a second position withinthe housing and is in thermal communication with the heat source to alesser extent relative to the first temperature sensor; and, a processorthat is disposed within the housing, is in electronic communication withthe first temperature sensor and the second temperature sensor, and usestemperature data from the temperature sensors to calculate a temperatureassociated with the analyte measurement component.

Also disclosed are systems comprising a housing that substantiallydefines an internal space; an analyte measurement component that iswithin the housing or proximate the housing; a first temperature sensorthat is disposed at a first position within the housing and is inthermal communication with a heat source; a second temperature sensorthat is disposed at a second position within the housing and is inthermal communication with the ambient environment outside of saidhousing to a greater extent relative to said first temperature sensor;and, a processor that is disposed within the housing, is in electroniccommunication with the first temperature sensor and the secondtemperature sensor, and uses temperature data from the temperaturesensors to calculate a temperature associated with the analytemeasurement component.

In yet another aspect, provided are methods for calculating atemperature associated with a test strip inserted in an analyteassessing system comprising measuring a first temperature at a firstposition that is in thermal communication with a heat source in theanalyte assessing system; measuring a second temperature at a secondposition in the analyte assessing system that is in thermalcommunication with the heat source to a lesser extent relative to thefirst position; and, using the measured first temperature and themeasured second temperature to calculate the temperature associated withthe test strip.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B respectively depict embodiments of the present inventionthat permit the displacement of heated air proximate the secondtemperature sensor.

FIG. 2 depicts an embodiment of the present invention in which thesecond temperature sensor is positioned proximate an opening in thehousing in order to decrease heat transfer resistance between the secondtemperature sensor and the ambient environment outside of the housing.

FIGS. 3A and 3B respectively illustrate a simplified thermodynamic modeland a steady-state thermodynamic electrical equivalent circuit that maybe used to describe certain aspects of the present invention.

FIGS. 4A and 4B show the results of an evaluation of an embodiment ofthe present invention that was configured to provide a convection systemthat permits air flow from the ambient environment that displaces heatedair proximate a second temperature sensor, and the temperature errorassociated with the test, respectively.

FIGS. 5A and 5B show the results of an evaluation of an embodiment ofthe present invention that was designed to increase the effectivesurface contact area between the second temperature sensor and theambient environment, and the temperature error associated with the test,respectively.

FIGS. 6A and 6B show the results of an evaluation of another embodimentof the present invention that was designed to increase the effectivesurface contact area between the second temperature sensor and theambient environment, and the temperature error associated with the test,respectively.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention may be understood more readily by reference to thefollowing detailed description taken in connection with the accompanyingfigures and examples, which form a part of this disclosure. It is to beunderstood that this invention is not limited to the specific products,methods, conditions or parameters described and/or shown herein, andthat the terminology used herein is for the purpose of describingparticular embodiments by way of example only and is not intended to belimiting of the claimed invention.

The use of one or more temperature sensors, for example, thermistors,thermometers, or thermocouple devices, to measure the ambienttemperature surrounding a biosensing instrument can provide informationthat may be used to improve the accuracy of measurement of one or moreanalytes in a biological sample. However, such methods fail to consider,and indeed may deliberately discount, the effect on the determination ofambient temperature by heat that is generated from one or morecomponents of the biosensing instrument. It has presently beendiscovered that the acquisition of temperature measurements at aposition within a biosensing instrument that is in thermal communicationwith a heat source, in addition to the measurement of temperature thatapproximates the ambient environment outside of the instrument, canimprove an instrument's ability to conduct accurate measurements of ananalyte in the test sample by allowing the instrument to compensate forthe actual temperature conditions affecting the reaction of the samplewith the strip's sensor assembly. The presently disclosed process of“dual temperature” measurement improves the ability of the biosensinginstrument to provide accurate readings regarding analyte levels, whichhas a positive effect on a user's ability to obtain the medicalinformation required to make appropriate and timely decisions regardingmedication, consultation with a doctor or nurse, or other treatmentoptions. Furthermore, the present invention permits a temperaturedetermination that is independent of the device orientation, powerfluctuation, and other factors that can skew temperature readings indevices in which sensors are only used to estimate ambient temperature,rather than measure both ambient temperature and temperature at aposition within a biosensing instrument that is in thermal communicationwith a heat source.

In one aspect of the present invention, provided are systems comprisinga housing that substantially defines an internal space; an analytemeasurement component that is within the housing or proximate thehousing; a first temperature sensor that is disposed at a first positionwithin the housing and is in thermal communication with a heat source; asecond temperature sensor that is disposed at a second position withinthe housing and is in thermal communication with the heat source to alesser extent relative to the first temperature sensor; and, a processorthat is disposed within the housing, is in electronic communication withthe first temperature sensor and the second temperature sensor, and usestemperature data from the temperature sensors to calculate a temperatureassociated with the analyte measurement component.

Also disclosed are systems comprising a housing that substantiallydefines an internal space; an analyte measurement component that iswithin the housing or proximate the housing; a first temperature sensorthat is disposed at a first position within the housing and is inthermal communication with a heat source; a second temperature sensorthat is disposed at a second position within the housing and is inthermal communication with the ambient environment outside of saidhousing to a greater extent relative to said first temperature sensor;and, a processor that is disposed within the housing, is in electroniccommunication with the first temperature sensor and the secondtemperature sensor, and uses temperature data from the temperaturesensors to calculate a temperature associated with the analytemeasurement component.

In yet another aspect, provided are methods for calculating atemperature associated with a test strip inserted in an analyteassessing system comprising measuring a first temperature at a firstposition that is in thermal communication with a heat source in theanalyte assessing system; measuring a second temperature at a secondposition in the analyte assessing system that is in thermalcommunication with the heat source to a lesser extent relative to thefirst position; and, using the measured first temperature and themeasured second temperature to calculate the temperature associated withthe test strip.

Unless otherwise specified, the description of a particular embodiment,feature, component, or functionality applies both to present methods andthe present systems. For example, reference to a “system” applies bothto the “analyte assessing systems” of the present methods and to the“systems” as separately claimed.

The present systems include a housing that substantially defines aninternal space. The housing may be made from any suitable material andmay adopt any appropriate configuration that can accommodate thosecomponents of the system that must be internal to the housing. Manybiosensing instruments have housings that comprise a plastic shellassembled from one or more molded parts. For example, the housing may bea shell comprising a first and a second half, one half forming the“upper” portion of a device in a horizontal resting position (such as ona tabletop, such that the long axis of the device is substantiallyparallel to the surface of the tabletop—if the device does not have along axis, then a “horizontal” orientation may refer to the restingposition of the device when in use, e.g., whereby the interactivecomponents such as the display, buttons, and the like, are facingupwards on the opposite face of the device that is in contact with thesurface, or may refer to the condition whereby the axis formed by animaginary line between the second temperature sensor and a heat sourceis substantially parallel to the surface), and the other half formingthe “lower” portion of the device, the two halves having been configuredto allow their secure attachment to one another in order to form anintegrated shell, and to accommodate internal components, componentsthat may be partially external to the housing (such as switches,interface buttons, display components, etc.), features necessary for theassembly of the housing (such as interlocking parts, or screw or rivetholes), batteries (i.e., the housing may include a battery port and/orbattery door), air vents, and the like. The housing may also feature oneor more coated sections that enhance the user's ability to grip thebiosensing instrument, such as rubber gripping portions on the outerlateral sides of the housing. Those skilled in the art will readilyappreciate the size, shape, and material parameters that may suitably beused to form a housing of an analyte measurement system.

The analyte measurement component is disposed within the housing orproximate the housing. In other words, the analyte measurement componentmay be partially or completely disposed within the housing, may bemounted or otherwise affixed to the housing, may be at least partiallydefined by the housing, or may be any combination thereof. The analytemeasurement component may include an aperture for receiving a test stripand can measure an analyte on the test strip, i.e., can measure ananalyte that is present within a biological sample on the test strip,thereby providing analyte measurement data, which can be communicated toanother component of the system. Analyte measurement components arefound in traditional biosensing instruments, for example, whereby theaperture is located at one end of the housing (which may in fact bemolded such as to define the aperture) and includes electricalcomponents that contact the inserted end of a test strip and receive theelectrical signals that have traveled to the inserted end of the teststrip from the end of the strip that holds the biological sample. Theaperture typically includes a groove or slot having the same width as atest strip, into which the test strip is inserted by the user. Theelectrical components interface with processing equipment inside thehousing, such as a microprocessor, to which the electrical componentssupply analyte measurement data corresponding to the signals receivedfrom the test strip. Various configurations for the analyte measurementcomponent will be readily appreciated by those having ordinary skill inthe art, who will recognize that the analyte measurement component ofthe present invention may be configured in a manner that is similar toanalyte measurement components of traditional biosensing instruments.

Each of the first and second temperature sensors may be any devicecapable of detecting static and/or dynamic temperature conditions. Thoseskilled in the art will readily appreciate that any of various types oftemperature sensors may be used, including, inter alia, thermistors,thermometers, or thermocouple devices. The first temperature sensor isdisposed at a first position within said housing and is in thermalcommunication with a heat source. Modern biosensing instruments aretypically compact devices, and often incorporate liquid crystal displayswith backlight, processors for data processing, radio-frequencycomponents for wireless communication, and many other electroniccomponents or subassemblies; such components consume power and theyresult in heat dissipation. The interior temperatures of compact deviceswith internal power dissipation can rise, sometimes significantly, abovethe ambient temperature, which can mean that a measurement oftemperature using a single internal thermistor may not be representativeof the actual ambient temperature. This can in turn influence analytereadings derived from a sample well or reaction zone of a test strip. Inaccordance with the present invention, the first temperature sensor isin thermal communication with a “heat source” (i.e., at least oneheat-generating component or subassembly that is included as part of abiosensing instrument) and can be used to account for the effect of theheat generated by the heat source on the determination of a temperatureassociated with the analyte measurement component. Information regardingthe use of temperature data from the first and second temperaturesensors in calculating a temperature associated with the analytemeasurement component is described infra. As used herein, “thermalcommunication” between two components or between a component and anenvironment preferably refers to the exposure of a component to heatconditions associated with the other component or with the environment;varying degrees of thermal communication may exist between components orbetween a component and a particular environment, such that with respectto a first component that emits heat or an environment possessingcertain temperature conditions, a second component may be in thermalcommunication with the first component or the environment to a lesser orgreater extent than a third component.

Unless otherwise specified, the first temperature sensor may comprisemore than one discrete temperature sensing device. Thus, more than onetemperature sensor in thermal communication with a heat source may bepresent. Where multiple “first” temperature sensors are present, eachmay be in thermal communication with the same heat source, each mayrespectively be in thermal communication with a different heat source,or some may be in thermal communication with one heat source while oneor more are in thermal communication with a different heat source.Accordingly, where multiple “first” temperature sensors are present, oneor more of the sensors may be disposed at or near the same positionwithin the housing, or each of the respective “first” temperaturesensors may be disposed at different positions within the housing(preferably each of the positions at which the “first” temperaturesensors are disposed are different from the location of any secondtemperature sensor).

Insulating material may be interposed between a first temperature sensorand a heat source. Insulating material comprises any substance orcondition that increases heat transfer resistance between the firsttemperature sensor and the heat source. For example, the insulatingmaterial may be rubber, plastic, metal, a foam (such as polyurethanefoam, styrofoam, and the like), or any other suitable material, manytypes of which are readily appreciated by those skilled in the art.Where multiple “first” temperature sensors are present, insulatingmaterial may be disposed between some or all of the “first” temperaturesensors and the heat source that is physically closest to a given“first” temperature sensor.

The second temperature sensor is disposed at a second position with thehousing and is in thermal communication with the heat source to a lesserextent relative to the first temperature sensor. For example, the secondtemperature sensor may be in thermal communication with the heat sourceto a lesser extent by virtue of spatial displacement (i.e., the distancebetween the second temperature sensor and the heat source is greaterthan the distance between the first temperature sensor and the heatsource), the existence of one or more physical barriers to heat betweenthe second temperature and the heat source (or the existence of greaternumbers of or more highly efficacious thermal barriers between thesecond temperature and the heat source as compared with the number orefficacy of the thermal barrier(s) between the first temperature sensorand the heat source), or any combination thereof. When “the heat source”comprises more than one heat-generating component or subassembly that isincluded as part of a biosensing instrument, the second temperaturesensor is in thermal communication with the combined amount of heatemitted from the more than one heat generating component or subassemblyto a lesser extent relative to the exposure of the first temperaturesensor to the combined amount of heat emitted from the more than oneheat generating component or subassembly.

In other embodiments of the present invention, the second temperaturesensor is disposed at a second position with the housing and is inthermal communication with the ambient environment outside of the systemhousing to a greater extent relative to the first temperature sensor. Insuch instances, there may be fewer physical thermal barriers, thermalbarriers that are less efficacious, or less spatial displacement betweenthe second temperature and the ambient environment, or there may be morethermal barriers, more efficacious thermal barriers, more spatialdisplacement between the first temperature sensor and the ambientenvironment as compared with the second temperature sensor, or anycombination thereof.

Unless otherwise specified, the second temperature sensor may comprisemore than one discrete temperature sensing device. Thus, more than onetemperature sensor that is in thermal communication with the heat sourceto a lesser extent relative to the first temperature sensor may bepresent. Where multiple “first” and “second” temperature sensors arepresent, with respect to a given “second” temperature sensor, suchsensor should be in thermal communication with a heat source to a lesserextent relative to at least one “first” temperature sensor, or should bein thermal communication with the ambient environment outside of thesystem housing to a greater extent relative to at least one “first”temperature sensor.

Insulating material may be interposed between a second temperaturesensor and a heat source. Insulating material comprises any substance orcondition that increases heat transfer resistance between the secondtemperature sensor and the heat source. For example, the insulatingmaterial may be rubber, plastic, metal, a foam (such as polyurethanefoam, styrofoam, and the like), or any other suitable material, manytypes of which are readily appreciated by those skilled in the art. Suchinsulating material may be present at the same time that insulatingmaterial is interposed between a first temperature sensor and a heatsource. Where multiple “second” temperature sensors are present,insulating material may be disposed between some or all of the “second”temperature sensors and the heat source that is physically closest to agiven “second” temperature sensor.

In other embodiments, insulating material may be interposed between afirst temperature sensor and a second temperature sensor. As providedabove, insulating material comprises any substance or condition that canserve to increase heat transfer resistance—here, as between a firsttemperature sensor and a second temperature sensor. Such insulatingmaterial may be present at the same time that (i.e., in the sameembodiment in which) insulating material is interposed between a firsttemperature sensor and a heat source, between a second temperaturesensor and a first temperature sensor, or both. Where multiple “first”and/or “second” temperature sensors are present, insulating material maybe disposed between only one of the “first” and one of the “second”temperature sensors, or between some or all of the “first” temperaturesensors and “second” temperature sensors.

Any combination of insulating material interposed between a firsttemperature sensor and a heat source, insulating material interposedbetween a second temperature sensor and a heat source, and insulatingmaterial interposed between a first temperature sensor and a secondtemperature sensor may be used in accordance with the present invention.

The temperature readings respectively performed by the first and secondtemperature sensors may occur simultaneously, or may take place atdifferent times relative to one another. Spatial and optionally temporalvariation between or among the first temperature sensor(s) and secondtemperature sensor(s) may be used to enhance the accuracy of thecalculation of a temperature associated with the analyte measurementcomponent, a test strip, or both.

The first and second temperature sensors are in electronic communicationwith a processor that is disposed within the housing and that usestemperature data from the temperature sensors to calculate a temperatureassociated with the analyte measurement component. Electroniccommunication refers to direct or indirect electronic communication,such that the processor may receive temperature data directly from oneor both of the first and second temperature sensors, or the processormay receive temperature data from a component that accepts data from oneor both of the first and second temperature sensors and transfers suchdata to the processor. The processor may also receive analytemeasurement data directly or indirectly from the analyte measurementcomponent, and may use the temperature data from the temperature sensorsto modulate the analyte measurement data. The processor that modulatesthe analyte measurement data using the temperature data may be a centralprocessing unit that receives the temperature data and the analytemeasurement data, respectively, from other processor components.

The second temperature sensor ideally provides temperature data thatsubstantially corresponds to the temperature of the ambient environmentoutside of the housing. To this end, the systems of the presentinvention may preferably adopt any configuration that permits exposureof the second temperature sensor to temperature conditions thatapproximate those of the ambient environment, even as, for practicalpurposes (such as to prevent damage to the sensor), the secondtemperature sensor is disposed within the housing.

In some embodiments, ambient air (that is, air from the ambientenvironment outside of the housing, or air having the same temperatureas the ambient environment outside of the housing) contacts the secondtemperature sensor and displaces heated air proximate the secondtemperature sensor. For example, the present systems may comprise afirst opening in the housing at a location proximate the secondtemperature sensor, a second opening at a second location in thehousing, a channel extending between the first opening and the secondopening and containing the second temperature sensor, wherein each ofthe openings place the channel in fluid communication with the ambientenvironment outside of the housing. “Fluid communication” between twolocations refers to the ability of air to flow therebetween. Likewise,the present systems may comprise a convection system that permits airflow from the ambient environment outside of the housing into at least aportion of the internal space, wherein the air flow displaces heated airproximate the second temperature sensor. As used herein, “heated air”refers to air having a temperature that is elevated beyond that of theambient environment outside of the housing of the biosensing instrument,wherein the elevation in temperature is typically attributable toheat-dissipation by one or more components of the biosensing instrument.A convection system can result from the creation of a temperaturedifferential between two locations within the housing. For example, theheat dissipated within the housing will typically be transferred to anupper portion of the housing and the lower portion of the housing may beisolated from the heat source using appropriate insulating material. Thetemperature difference between the lower portion of the housing and theupper portion of the housing creates airflow.

FIG. 1A depicts a side view embodiment of the present invention (thenear side wall of the housing is omitted in order to allow viewing ofcomponents inside of the housing) whereby ambient air enters the housingvia an opening, flows over the second temperature sensor, and displacesheated air proximate the second temperature sensor so that the heatedair flows out of a second opening in the housing. The path of the airflow (arrows) corresponds to the contours of a channel that ispreferably oriented substantially vertically within a biosensinginstrument when that instrument is placed in a horizontal, restingposition on a flat surface. In FIG. 1A, insulating material, such asthat described supra, is used to increase heat transfer resistancebetween the second temperature sensor and one or more heat sourceslocated in other portions of the housing (not shown), and conductingmaterial, such as metal, is used to provide better heat conductivitythan the portion of the housing proximate the second temperature sensorto create a temperature differential within the housing and therebyfurther encourage heat flow away from the second temperature sensor.

In other embodiments, one or more heat sources generate heat for formingthe heated air that is displaced by ambient air. Thus, one or more heatsources may generate heated air in order to allow the formation of aconvection system that permits air flow from the ambient environmentoutside of the housing and the consequent displacement of heated airproximate the second temperature sensor. In some embodiments, heated airis formed by heat transferred from a heat source via a transfer elementthat contacts the heat source. For example, heat that is transferredfrom a heat source (such as a microprocessor) via a circuit board canform the heated air. As provided above, heat sources associated with abiosensing instrument may include liquid crystal displays withbacklight, processors for data processing, radio-frequency componentsfor wireless communication, and many other power-consuming electroniccomponents or subassemblies. In some embodiments, the channel throughwhich ambient air from the environment outside of the housing may be inat least partial thermal communication with a heat source. FIG. 1Bdepicts an embodiment wherein the channel is in thermal communicationwith a heat source (e.g., a microprocessor—not shown) via a printedcircuit board (PCB) on which the heat source is mounted; the PCB is notseparated from the channel by insulating material, and in fact generatesheated air that is displaced by air flowing from the ambient environmentoutside of the housing. The path of the air flow (arrows) corresponds tothe contours of a channel that is preferably oriented substantiallyvertically within a biosensing instrument when that instrument is placedin a resting position on a flat surface. An arrangement of the varietydepicted in FIG. 1B may obviate the need to use conductive material(e.g., as in FIG. 1A). In addition, in accordance with such embodiments,the aperture into which the strip is inserted may function as the“second opening” through which heated air that is displaced from thesecond temperature sensor exits the channel, thereby obviating the needto provide a separate “second opening”.

The present systems may adopt any other configuration that permits theexposure of the second temperature sensor to temperature conditions thatapproximate those of the ambient environment. In certain embodiments,the present systems may be configured to reduce the heat transferresistance between the second temperature sensor and the ambientenvironment outside of said housing. In other embodiments, the presentsystems may be configured to increase the effective contact surface areabetween the second temperature sensor and the ambient environmentoutside of the housing. For example, the second temperature sensor maybe positioned proximate an opening in the housing. The “contact” betweenthe second temperature sensor and the ambient environment need not bedirect, and may be mediated by a component having low heat resistance.For example, the second temperature sensor may be positioned proximatean opening in the housing, and heat conductive material may be disposedbetween the second temperature sensor and the opening in the housing.“Heat conductive material” may refer to any material that provides alower heat transfer resistance than the material from which the housingis substantially formed; for example, the heat conductive material maybe metal (such as aluminum, copper, steel, silver, or a metal alloy likebrass, and the like), plastic, glass, or any other suitable material.Alternatively, the heat conductive material may be the same material asthat from which the housing is substantially formed, but having athinner cross-section so that heat transfer resistance across the heatconductive material is decreased relative to the heat transferresistance across a portion of the housing. The second temperaturesensor may be mounted on the heat conductive material that is disposedbetween the sensor and the opening in the housing. In some embodiments,a “heat sink” material may be disposed between the heat conductivematerial and the sensor. The heat sink material may be any substancehaving low heat transfer resistance such as to minimize the heattransfer path between the ambient environment outside of the housing andthe second temperature sensor. Heat sink materials may be fluid orpaste-like substances that increase the thermal conductivity of athermal interface, for example, by compensating for the irregularsurfaces of the components that are linked by the heat sink material.Examples include thermal grease, thermal paste, and other materials thatwill be readily appreciated by those skilled in the art.

The second temperature sensor, opening in the housing, and heatconductive material may be at least partially isolated from theremainder of the internal space defined by the housing. The isolation ofthe second temperature sensor, opening in the housing, and heatconductive material may comprise thermal isolation be accomplishedthrough the use of insulating material as defined above (i.e., anymaterial that increases heat transfer resistance). FIG. 2 depicts ahorizontally-oriented side view of an embodiment of the presentinvention as it would appear if the system were placed in a restingposition on a flat surface (i.e., such that the long axis of the systemis substantially parallel to the flat surface; if the system did nothave a long axis, “horizontal” orientation may refer to the conditionwhereby the axis formed by an imaginary line between the secondtemperature sensor and a heat source is substantially parallel to thesurface); the near side wall of housing 3 is omitted in order to allowviewing of internal components. This embodiment includes an opening 1 inhousing 3, over which a plate 5 of heat conductive material is disposed.Second temperature sensor 7 is mounted on plate 5, and these componentsare enclosed within insulating material 9, 11 in order to at leastpartially thermally isolate them from other portions of the internalspace M₁, M₂. Plate 5 increases the effective contact surface areabetween the ambient environment A outside of the housing 3 and thesecond temperature sensor 7, which in turn lowers the heat transferresistance between the ambient environment A and second temperaturesensor 7.

If the orientation of the system is changed, for example, if the systemwere oriented vertically with second temperature sensor 7 at the “top”(rather than at the “side”, as shown in FIG. 2), then it is possiblethat heat emitted from heat source S (actual component not shown) couldreach second temperature sensor 7 by convection to a greater extent thanwhen the system is oriented horizontally, and thereby introduce errorinto the temperature readings performed by the second temperature sensor7. In order to minimize the effects of changes in orientation of thesystem, an optional heat convection barrier 13 comprising insulatingmaterial can be used to increase heat transfer resistance between M₁ (inwhich both the first temperature sensor 8 and the second temperaturesensor 7 are located) and M₂ (in which heat source S is disposed). Asdemonstrated infra in Example 2, the inclusion of a heat convectionbarrier between a portion of the internal space of the system in which aheat source is located and the portion of the internal space of thesystem can correct for the effects of heat convection when theorientation of the system is changed, e.g., from horizontal to vertical,or vice versa.

The first and second temperature sensors are in electronic communicationwith a processor that is disposed within the housing and usestemperature data from the temperature sensors to calculate a temperatureassociated with the analyte measurement component. The system may thencompensate for the calculated temperature associated with the analytemeasurement component during a measurement of an analyte on a teststrip. For example, the measurement of an analyte on a test strip mayresult in the acquisition of analyte measurement data that may bemodulated in order to account for the temperature data acquired from thefirst and second temperature sensors. The calculation of a temperatureassociated with the analyte measurement component, the receipt ofanalyte measurement data, and any compensation for the calculatedtemperature associated with the analyte measurement component may beperformed by separate processors that are in electronic communicationwith any of the first temperature sensor, second temperature sensor, andanalyte measurement component, or each of these functions may beperformed by a single multifunction processor. As used herein,“electronic communication” may be mediated by physical means (e.g.,circuits), or may be “wireless”. The processor that receives the analytemeasurement data may be the same processor that receives temperaturedata from the first and second temperature sensors. Alternatively, theprocessor that modulates the analyte measurement data using thetemperature data may be a central processing unit that receives thetemperature data and the analyte measurement data, respectively, fromother processor components. Various configurations for the processorsand other components of the present systems will be readily appreciatedamong those skilled in the art, and any suitable configuration may beused in accordance with the present invention.

A simplified steady-state thermodynamic model may be used to describethe considerations undertaken pursuant to the present systems in orderto calculate a temperature associated with the analyte measurementcomponent and/or a test strip, and/or compensate for the calculatedtemperature associated with the analyte measurement component and/or atest strip during a measurement of an analyte. FIGS. 3A and 3Brespectively provide a simplified thermodynamic model and a steady-statethermodynamic electrical equivalent circuit, in which the followingabbreviations are employed:

Symbol Meaning P Power dissipation inside the device M Main area of theinternal space within the housing where the main heat sources arelocated. S Area of the housing where the second temperature sensor S ispositioned. The temperature values of S and M are the basis for thecalculation of the temperature associated with the analyte measurementcomponent TM Temperature measured by the first temperature sensor in thearea M within the housing TS Temperature measured by the secondtemperature sensor in the area S within the housing TA Actual ambienttemperature RMA Heat transfer resistance between the area M and theambient environment outside of the housing RMS Heat transfer resistancebetween the area M and the second temperature sensor S RSA Heat transferresistance between the second temperature sensor S and the ambientenvironment outside of the housingIn a dynamic model there are heat capacitances for the housing and thetemperature sensors that can be modeled as capacitors in the electricalequivalent model (FIG. 3B). In the steady state these capacitors arehigh impedance and can be ignored. Thus, the temperature difference(TS−TA) is calculated from the difference of (TM−TA) according to therelationship of RSA and RMS, so that the following formulas apply:

$\begin{matrix}\begin{matrix}{{{TS} - {TA}} = {\frac{RSA}{{RSA} + {RMS}} \cdot \left( {{TM} - {TA}} \right)}} & \left( {{For}\mspace{14mu}{steady}\mspace{14mu}{state}} \right)\end{matrix} & (1) \\\begin{matrix}{K = \frac{RSA}{{RSA} + {RMS}}} & \left( {{For}\mspace{14mu}{steady}\mspace{14mu}{state}} \right)\end{matrix} & (2) \\{K\begin{matrix}{= \frac{\left( {{TS} - {TA}} \right)}{\left( {{TM} - {TA}} \right)}} & \left( {{For}\mspace{14mu}{steady}\mspace{14mu}{state}} \right)\end{matrix}} & (3) \\\begin{matrix}{{TA} = {{TS} + {\frac{K}{K - 1}\left( {{TM} - {TS}} \right)}}} & \left( {{For}\mspace{14mu}{steady}\mspace{14mu}{state}} \right)\end{matrix} & (4)\end{matrix}$

K is a constant that depends on the thermodynamic structure of thesystem as defined by equation (2). In practice, this constant isestimated by a series of temperature measurements of TM, TS and TA usingequation (3). This constant is programmed into software used by thesystem. Then, using equation (4), the ambient temperature is estimatedusing TM, TS and K. As it is seen, the smaller the K, then TS is betterrepresentative of the ambient temperature.

In accordance with the present invention, a processor may calculate thetemperature (TA) associated with the analyte measurement component byperforming a calculation according to formula (I)

$\begin{matrix}{{TA} = {{TS} + {\frac{K}{K - 1}\left( {{TM} - {TS}} \right)}}} & (I)\end{matrix}$wherein TS is the temperature measured by said second temperaturesensor, TM is the temperature measured by the first temperature sensor,and K is defined by

$K = \frac{\left( {{TS} - {TA}} \right)}{\left( {{TM} - {TA}} \right)}$wherein TS is the temperature measured by the second temperature sensor,TA is the actual temperature of the ambient environment outside of saidhousing, and TM is the temperature measured by the first temperaturesensor.

EXAMPLES Example 1 Convection System

A climate chamber was used to test an exemplary system designed toprovide a convection system for increasing the exposure of the secondtemperature sensor to air from the ambient environment. Foam rubberinsulating material was used to form a chamber enclosing the secondtemperature sensor in order to increase heat transfer resistance betweenthe second temperature sensor from the remainder of the internal spaceof the system defined by the housing. Openings in the housing were usedto permit air flow from the ambient environment into the chamber and topermit the displacement of heated air proximate the second temperaturesensor. The first temperature sensor was positioned on a circuit board,and the internal space inside of the housing was divided by insulatingmaterial into two main portions: M1, in which the first temperaturesensor, circuit board, and the chamber containing the second temperaturesensor were located, and M2, in which a heat source comprising aresistor having a power dissipation of approximately 1.4 W was located.The heat source was switched on and off during the experiment tosimulate the behavior of the system during variable heat dissipationperiods such as would occur during normal operation of a biosensinginstrument. Temperature readings were acquired at 5 second intervals.FIG. 4A depicts results wherein TS represents the temperature readingsacquired by the second temperature sensor, TM represents the temperaturereadings acquired by the first temperature sensor, TS Estimationrepresents the ambient temperature as calculated by the system using thefirst and second temperature sensor readings, and TA is the actualambient temperature as separately measured within the test chamber. FIG.4B shows the temperature error in the calculation of the temperature ofthe ambient environment outside of the housing (which is equivalent to atemperature associated with an analyte measurement component, a teststrip, or both). Results are shown in 5 second intervals.

Example 2 System Increasing Effective Surface Contact Area with AmbientEnvironment

A climate chamber was used to test an exemplary system designed toincrease the effective surface contact area between the secondtemperature sensor and the ambient environment. The experimental systemincluded a housing having an opening over which a brass plate having athickness of about 0.5 mm was placed. The second temperature sensor wasmounted on the brass plate and the sensor/plate arrangement was enclosedwithin a chamber defined by insulating material. The insulating materialdefining the chamber was a layer of plastic housing material, i.e., alayer of the same type of plastic used to form the housing. A resistorwith an external power supply that provided a power dissipation of about1.4 W was placed within the interior space defined by the housing,outside of the chamber in which the sensor/plate arrangement wasenclosed. The heat source was switched on and off during the experimentto simulate the behavior of the system during variable heat dissipationperiods such as would occur during normal operation of a biosensinginstrument. Temperature readings were acquired at 5 second intervals,the maximum period during which the resistor was operational was 0.5hours.

FIG. 5A depicts results wherein TS represents the temperature readingsacquired by the second temperature sensor, TM represents the temperaturereadings acquired by the first temperature sensor, TA Estimationrepresents the ambient temperature as calculated by the system using thefirst and second temperature sensor readings, and TA is the actualambient temperature as separately measured within the test chamber.

FIG. 5B shows the temperature error in the calculation of thetemperature of the ambient environment outside of the housing (which isequivalent to a temperature associated with an analyte measurementcomponent, a test strip, or both). Results are shown in 5 secondintervals.

It was determined that the major sources of error with respect to theabove-described system included sudden changes in ambient temperature,power dissipation fluctuations inside the system, and the orientation ofthe system relative to the ground. Large error spikes were observed whenthe ambient temperature changes rapidly; however, such rapid changes inambient temperature are not typically encountered during ordinary use ofa biosensing instrument. Thus, the areas of interest with respect totemperature error are fluctuations in heat dissipation inside thesystem, and changes in system orientation.

The measurements depicted in the FIGS. 5A and 5B were made while thesystem was oriented horizontally, i.e., while at rest on a flat surfacewith the long axis of the device oriented substantially parallel to thesurface. When the system was moved to a vertical orientation (i.e., withthe long axis of the device oriented substantially perpendicular to thesurface—if the device did not have a long axis, “vertical” orientationwould refer to the condition whereby the axis formed by an imaginaryline between the second temperature sensor and a heat source issubstantially perpendicular to the surface), the simplified thermalmodel showed additional errors due to heat convection towards the cavitythat enclosed the second temperature sensor (results not shown). Toreduce the effect of heat convection when the system is orientedvertically, a heat convection barrier was incorporated into the system(see, e.g., item 13 in FIG. 2), separating the interior space into twoportions, one of which contained the heat source, and the other of whichcontained the cavity enclosing the sensor/plate arrangement. The firsttemperature sensor was located in the same space within the housing(i.e., on the same side of the heat convection barrier) in which thecavity enclosing the sensor/plate arrangement was located. The firsttemperature sensor was located inside a microprocessor mounted on aprinted circuit board (PCB), which was disposed such that a portion ofthe board was on one side of the heat convection barrier, and theremaining portion of the board was on the opposite side of the heatconvection barrier. The heat source (a resistor) was mounted on theportion of the PCB that was on the opposite side of the heat convectionbarrier from the first temperature sensor. Instead of a single PCB, analternative arrangement may include two separate PCBs linked by aboard-to-board connector, wherein the respective PCBs are on oppositesides of the heat convection barrier. The system with the heatconvection barrier was tested in both the horizontal and verticalorientation, and it was found that the barrier effectively eliminatedthe effect of system orientation on the temperature calculation. Resultsare shown in FIG. 6A, wherein the peaks labeled “H” correspond totemperature readings obtained while the system was in the horizontalorientation, peaks labeled “V” correspond to temperature readingsobtained while the system was in the vertical orientation, TS representsthe temperature readings acquired by the second temperature sensor, TMrepresents the temperature readings acquired by the first temperaturesensor, TA Estimation represents the ambient temperature as calculatedby the system using the first and second temperature sensor readings,and TA is the actual ambient temperature as separately measured withinthe test chamber.

FIG. 6B shows the temperature error in the calculation of thetemperature of the ambient environment outside of the housing (which isequivalent to a temperature associated with an analyte measurementcomponent, a test strip, or both), wherein the peaks labeled “H”correspond to error in the temperature readings obtained while thesystem was in the horizontal orientation, and peaks labeled “V”correspond to error in the temperature readings obtained while thesystem was in the vertical orientation. Results are shown in 5 secondintervals.

The preceding experiments demonstrate that, inter alia, the measurementof temperature associated with an analyte measurement process isimproved using the present dual sensor approach, and that accuratetemperature measurement can occur regardless of device orientation andfluctuations in power dissipation. The present approach also reduces theamount of time a user must wait to use the biosensing instrumentmeasurement after the instrument has been moved between locations thatare respectively characterized by different ambient temperatureconditions. Such advantages improve the ability of the biosensinginstrument to provide accurate readings regarding analyte levels. Inaddition, the systems described herein are suitable for use inconnection with modern handheld devices that feature a compact design.

The disclosures of each patent, patent application, and publicationcited or described in this document are hereby incorporated herein byreference, in their entirety.

As employed above and throughout the disclosure, the following terms andabbreviations, unless otherwise indicated, shall be understood to havethe following meanings. In the present disclosure the singular forms“a,” “an,” and “the” include the plural reference, and reference to aparticular numerical value includes at least that particular value,unless the context clearly indicates otherwise. Thus, for example, areference to “a heat source” is a reference to one or more of such heatsources and equivalents thereof known to those skilled in the art, andso forth. When values are expressed as approximations, by use of theantecedent “about,” it will be understood that the particular valueforms another embodiment. As used herein, “about X” (where X is anumerical value) preferably refers to ±10% of the recited value,inclusive. For example, the phrase “about 8” preferably refers to avalue of 7.2 to 8.8, inclusive; as another example, the phrase “about8%” preferably refers to a value of 7.2% to 8.8%, inclusive. Wherepresent, all ranges are inclusive, divisible, and combinable. Forexample, when a range of “1 to 5” is recited, the recited range shouldbe construed as including ranges “1 to 4”, “1 to 3”, “1-2”, “1-2 and4-5”, “1-3 and 5”, and the like.

What is claimed:
 1. A method for calculating temperature associated witha test strip inserted in an analyte assessing system comprising:measuring a first temperature at a first position that is in thermalcommunication with a heat source in said analyte assessing system;measuring a second temperature at a second position in said analyteassessing system that is in thermal communication with said heat sourceto a lesser extent relative to said first position; and, using themeasured first temperature and the measured second temperature tocalculate the temperature associated with said test strip, wherein saidfirst temperature is measured by a first temperature sensor and saidsecond temperature is measured by a second temperature sensor; saidsystem comprises a housing that encloses said first temperature sensorand said second temperature sensor, a first opening in said housing at alocation proximal to said second temperature sensor, a second opening ata second location in said housing, and a channel extending between saidfirst opening and said second opening and containing said secondtemperature sensor, wherein each of said openings place said channel influid communication with the ambient environment outside of saidhousing, and, ambient air contacts said second temperature sensor anddisplaces heated air proximate said second temperature sensor.
 2. Themethod according to claim 1 wherein insulating material is interposedbetween said second temperature sensor and said heat source.
 3. Themethod according to claim 1 wherein insulating material is interposedbetween said second temperature sensor and said first temperaturesensor.
 4. The method according to claim 1 further comprisingcompensating for said calculated temperature associated with said teststrip during a measurement of an analyte on said test strip.
 5. Themethod according to claim 1 wherein said temperature associated withsaid test strip is calculated by a processor housed within said system.6. The method according to claim 5 wherein said processor is inelectronic communication with a first temperature sensor that measuressaid first temperature, and with a second temperature sensor thatmeasures said second temperature.
 7. The method according to claim 5wherein said processor calculates said temperature (TA) associated withsaid test strip by performing a calculation according to formula (I)$\begin{matrix}{{TA} = {{TS} + {\frac{K}{K - 1}\left( {{TM} - {TS}} \right)}}} & (I)\end{matrix}$ wherein TS is the temperature measured by said secondtemperature sensor, TM is the temperature measured by the firsttemperature sensor, and K is defined by$K = \frac{\left( {{TS} - {TA}} \right)}{\left( {{TM} - {TA}} \right)}$wherein TS is the temperature measured by the second temperature sensor,TA is the actual temperature of the ambient environment outside of saidhousing, and TM is the temperature measured by the first temperaturesensor.
 8. The method according to claim 1 wherein said housingsubstantially defines an internal space, and wherein said secondtemperature sensor is positioned proximate an opening in said housing.9. The method according to claim 8 wherein said system is configured toreduce the heat transfer resistance between the second temperaturesensor and the ambient environment outside of said housing.
 10. Themethod according to claim 8 wherein said system further comprisesinsulating material that at least partially isolates said secondtemperature sensor, said heat conductive material, and said opening fromthe remainder of the internal space of said housing.
 11. The methodaccording to claim 8 wherein heat conductive material is disposedbetween said second temperature sensor and said opening in said housing.12. The method according to claim 11 wherein said second temperaturesensor is mounted on said heat conductive material.
 13. The methodaccording to claim 11 wherein said heat conductive material comprisesmetal or plastic.
 14. A method for calculating temperature associatedwith a test strip inserted in an analyte assessing system comprising:measuring a first temperature at a first position that is in thermalcommunication with a heat source in said analyte assessing system;measuring a second temperature at a second position in said analyteassessing system that is in thermal communication with said heat sourceto a lesser extent relative to said first position; and, using themeasured first temperature and the measured second temperature tocalculate the temperature associated with said test strip, wherein saidtemperature associated with said test strip is calculated by a processorhoused within said system, and, said processor calculates saidtemperature (TA) associated with said test strip by performing acalculation according to formula (I) $\begin{matrix}{{TA} = {{TS} + {\frac{K}{K - 1}\left( {{TM} - {TS}} \right)}}} & (I)\end{matrix}$ wherein TS is the second temperature, TM is the firsttemperature, and K is defined by$K = \frac{\left( {{TS} - {TA}} \right)}{\left( {{TM} - {TA}} \right)}$wherein TS is the second temperature, TA is the actual temperature ofthe ambient environment outside of said housing, and TM is the firsttemperature.
 15. The method according to claim 14 wherein said processoris in electronic communication with a first temperature sensor thatmeasures said first temperature, and with a second temperature sensorthat measures said second temperature.
 16. The method according to claim14 wherein said first temperature is measured by a first temperaturesensor and said second temperature is measured by a second temperaturesensor, and wherein said first temperature sensor and said secondtemperature sensor are each housed within said system.
 17. The methodaccording to claim 16 wherein insulating material is interposed betweensaid first temperature sensor and said heat source.
 18. The methodaccording to claim 16 wherein insulating material is interposed betweensaid second temperature sensor and said heat source.
 19. The methodaccording to claim 16 wherein insulating material is interposed betweensaid second temperature sensor and said first temperature sensor. 20.The method according to claim 16 wherein said system comprises a housingthat encloses said first temperature sensor and said second temperaturesensor and substantially defines an internal space, and wherein saidsecond temperature sensor is positioned proximate an opening in saidhousing.
 21. The method according to claim 20 wherein said system isconfigured to reduce the heat transfer resistance between the secondtemperature sensor and the ambient environment outside of said housing.22. The method according to claim 20 wherein said system furthercomprises insulating material that at least partially isolates saidsecond temperature sensor, said heat conductive material, and saidopening from the remainder of the internal space of said housing. 23.The method according to claim 20 wherein heat conductive material isdisposed between said second temperature sensor and said opening in saidhousing.
 24. The method according to claim 23 wherein said secondtemperature sensor is mounted on said heat conductive material.
 25. Themethod according to claim 23 wherein said heat conductive materialcomprises metal or plastic.